With technology advances, various electronic products are widely used nowadays. Conductive circuits are important elements for the electronic products, and hence a method for fabricating conductive circuits of the electronic products is continuously being developed and improved.
In recent years, the application of ink printing techniques to manufacture a conductive circuit has caught much attention. CN 1946880 B discloses a method of providing a pattern of a metal on a non-conductive substrate by virtue of ink printing techniques. The method includes the steps of applying a catalytic ink having a source of catalytic metal ions (such as palladium ions and gold ions) in a desired pattern on a surface of the non-conductive substrate; reducing the source of catalytic metal ions to its associated metal with a suitable reducing agent; depositing an electroless metal layer on the pattern of catalytic ink; and plating an electrolytic metal on the electroless metal layer to produce the desired pattern of metal on the substrate.
CN 101640979 A discloses another method of manufacturing a conductive circuit using ink printing techniques. The method disclosed therein includes the steps of printing a catalytic ink containing silver salt solution (such as a silver nitrate solution, a silver sulfate solution, and a silver acetate solution) to form a circuit pattern on a substrate; irradiating the circuit pattern to reduce silver ions contained in the silver salt solution to silver metals, thereby forming a circuit precursor; and plating a conductive metal layer on the circuit precursor to obtain the conductive circuit.
However, the metal ions (such as palladium, silver and gold ions, etc.) in the solution (i.e., in the liquid state) are usually unstable, and tend to undergo undesired reactions. Moreover, if the metal ions are in a non-liquid state or exposed to high temperatures, the reactivity thereof would be greatly reduced. Given this, the metal ions included in the catalytic ink as disclosed in the aforesaid prior art, when applied onto the substrate, must be immediately reduced into a catalytic metal in order to avoid occurrence of the aforesaid undesired reaction or reduced reactivity of the metal ions.
Therefore, the applicants have endeavored to develop a catalyst including catalytic metal ions that are stable and do not require conducting of a reduction reaction immediately when applied onto a substrate.